Compensated shunt type snap action device



Nov. 16, 1965 H. G. snBERG COMPENSATED SHUNT TYPE SNAP ACTION DEVICE Filed Deo. 21, 1961 ETI ATTORNEYS United States Patent O 3,218,411 COMPENSATED SHUNT TYPE SNAP ACTIGN IEEVICE I-Iemming G. Siiberg, Westfield, NJ., assignor to Tung- Sol Electric Inc., a corporation of Delaware Filed Dec. 21, 1961, Ser. No. 161,168 7 Claims. (Cl. 20S-113) The present invention relates to snap action devices of the type wherein an expansible pull wire or ribbon, when cold, holds a contact carrying spring vane or the like in one circuit controlling position and, when expanded by passage of current therethrough, permits the vane to snap to another circuit controlling position. Such type of device is used extensively for flashing lights such as automobile turn signal lamps. For such use it is desirable that the rate of flashing, and also the ratio of the on and off periods of the controlled lamps, be relatively constant with change in supply voltage. In prior art devices, whether the pull ribbon is in series with the lamps when the lamps are on (series device) or is shunted from the circuit when the lamps are on (shunt device) the rate of flashing tends to increase with increase in supply voltage. In the prior art series devices, with increase in voltage the ratio of on to oit decreases whereas in the prior art shunt devices, with increase in voltage the ratio of on to oft increases.

The snap action device of the present invention maintains constant rate with change in voltage by providing automatic change in bias of the vane and insures constant speed and ratio by combining features of both the series and shunt type devices. More specifically the new liasher includes two pull means, one adapted to be shunted in the on period of the controlled lamps and the other being in series with the lamp load during the on period. With this arrangement, one pull means is cooling and contracting while the other is expanding with the result that the longer time to cool from high temperature is compensated by the shorter time to heat at such temperature. That one of the pull means which is in the circuit during on time serves to provide part of the bias of the vane, weakening the bias as the voltage increases and thereby tending to maintain constant the ashing rate.

For a better understanding of the invention and of a specific embodiment thereof, reference may be had to the accompanying drawing of which:

FIG. 1 is a vertical sectional view of a asher embodying the invention;

FIG. 2 is a view of the flasher of FIG. 1 taken at right angles thereto;

FIGS. 3 and'4 are detail sectional views taken on the lines 3-3 and 4-4, respectively of FIG. 2; and

FIG. 5 is a detail sectional view taken on the line 5 5 of FIG. 1.

In the device illustrated in the drawing the flasher elements are mounted on a disc 2 of insulating material from the underside of which depend prong terminals 4 and 6. Claws of terminal 4 extend through the base and serve to clamp to the base a frame element 8. The frame 8 has an upstanding section 8a provided with spaced shoulders 12, 12 (see FIG. 4) against which is held the lower portion of a vane 16 of resilient material. The Vane 16 spans the shoulders 12, 12 and is held in engagement therewith by a screw 18 which extends through a hole in the vane and threads into the frame section 8a. A leaf spring 20 is interposed between the head of the screw 18 and the vane.

3,218,411 Patented Nov. 16, 1965 ice The vane 16, in the particular embodiment illustrated in the drawing, is of the type disclosed and claimed in applicants copending application Serial No. 65,789, tiled October 28, 1960 now U.S. Patent No. 3,052,780, dated September 4, 1962. It is rectangular in shape and is transversely creased and bent at 22. The screw 18 in conjunction with the shoulders' 12 curves the vane about a longitudinal axis perpendicular to the bend 22, tending to straighten the vane. The upper free end of spring 20 overlies the bend 22 on the convex side thereof and mounted on such free end of the spring 20 is one leg of an L-shaped angle member 24 to the other leg of which is secured an end of a tensioned pull wire 26. The force applied to the vane by the wire through angle member 24 is in a direction to supplement the action of screw 18 and shoulders 12 in straightening the vane and moving the free end thereof to the right as viewed in FIG. 1.

Frame 8 has an upper horizontal arm 8b which is provided with a hole 28. Pull wire 26 extends through the hole 28 and is anchored therein by an insulating bead 30. Beyond bead 30, wire 26 is coiled to form a ballast resistor 32 the other end of which is fastened to one leg 0f a bracket 34, supported by the frame 8 but electrically insulated therefrom. Bracket 34 is electrically connected to terminal 6 by a connector 36. Bracket 34 is positioned and held between flanges (see FIG. 5) of frame 8, spacers 38 of mica or other insulating material being provided on each surface of the bracket to insulate it from the frame. An upper leg of bracket 34 extends through an opening 40 in the frame and carries at its extremity a contact 42. At the upper or free end of vane 16 there is a tensioned pull ribbon 44 which is welded to opposite edges of the vane and extends parallel to the bend 22. The pull ribbon 44 carries a contact 46 at its central point which is aligned with contact 42. The tension in pull ribbon 44 curves the free end of the vane about the longitudinal axis of the vane and oppositely to the curvature introduced by the screw 18 and shoulders 12. When the tension in pull wire 26 is released and when the pull ribbon 44 is cold, Contact 46 engages contact 42.

Before describing the operation of the above described device, the correspondence between the above described elements and those previously mentioned will be pointed out. In the device of the drawing the two pull means are the pull wire 26 and the pull ribbon 44. The pull ribbon 44 is connected to the vane in such manner as to provide part of the initial bias of the vane toward contact closing position. The crease or bend 22 provides the remaining bias toward contact closing position. The screw 18 and shoulders 12 provide means for initial and final adjustment. Pull ribbon 44 (when the contact thereon is in engagement with the xed contact) provides part of the shunt about the pull wire 26, the vane and bracket 34 completing the shunt about pull wire 26 and resistor 32. Thus the device may be considered as a series-shunt type device or as an automatically compensated shunt type device.

In the operation of the device the parts are initially adjusted by screw 18 so that in the cold condition of the pull wire and pull ribbon, contacts 42 and 46 are closed. If now a circuit including a source of energy, which may be a car carried battery of nominally 12 volts, and a lamp load is connected across terminals 4 and 6, current ows on the first cycle from terminal 4, through frame 8, vane 16, pull ribbon 44, contacts 42 and 46, bracket 34 and wire 36 to terminal 6. This circuit heats the ribbon 44, causing it to expand immediately to relieve initial stress and permit the vane to snap to contact open position. The current then flows from frame 8 through spring 20, anchor member 24, pull wire 26, resistor 32 and connector 36 to terminal 6. Because of the inclusion of resistor 32 and pull wire 26 in the circuit the current will be insuicient to light the lamps but sutiicient to heat the wire 26 and cause it to expand suiciently to permit the upper end of vane 16 to move under the bias introduced by crease 22 and pull ribbon 44 which has now been cooled and contracted into position to close contacts 42 and 46. In the closed position of the contacts, pull wire 26 and resistor 32 are shunted, current flowing through the vane 16, through the two halves of pull ribbon 44, contacts 42 and 46, though bracket 34 and connecter 36 to terminal 6. This current will be suliicient to light the lamps. The lamps will remain on until the resulting expansion of pull ribbon 44 and the concurrent contraction of pull wire 26 causes the vane to snap into contact open position. The cycle then repeats. Thus during the on cycle, the pull ribbon 44 expands and changes the bias in the vane and consequently the snap point of the same. The snap force becomes less and the asher opens sooner than in conventional shunt type operation. If the current through the pull ribbon falls appreciably, due to failure of one or more lamps of the load the tension in the pull ribbon will remain high enough to Imaintain the contacts closed. Continuous illumination of a pilot lamp in the lamp circuit will thus be a positive indication of lamp failure.

If the voltage of the source increases the current both -in the on and off condition of the lamps will increase through the device and the temperature of the pull wire 26 and of the pull ribbon 44 will increase. At such higher temperature the tension of pull wire 26 is less and therefore there is a tendency for the off period of the lamps to be short, but on the other hand at such higher temperature it takes the pull ribbon 44 longer to contract tending to increase the off period of the lamps. Thus as the changing from off `to on i:s -a lfunction of tension of both the pull wire 26 and of the pull ribbon 44 automatic compensation for the change in the length of the off period with change of temperature is effected. Also at such higher temperature it takes longer for the pull wire 26 to contract, therefore there is a tendency for the lamps to stay on longer but as the tension in pull ribbon 44 is less at such higher temperature the bias on the vane is weakened, and this tends to shorten the on period. Thus automatic compensation for change in the on period with change in temperature is effected. Consequently as both the on and off periods are maintained substantially constant by the opposing actions of the two pull means of the device the rate of tiashing will also remain constant with change in temperature. Furthermore, with increase in voltage (that is current) the contact spacing increases, due to `changed bias in the vane which allows further travel of the vane, thus also keeping rate or speed of the device constant.

The invention has now been described with reference to one specific construction of flasher. Obviously the invention could be embodied in flashers having other types of wire controlled movable blades. Although in the specific embodiment of the invention illustrated and described both pull means are directly heated by current therethrough, obviously either or both of the pull means could be indirectly heated as by heating coils. Other variations within the scope of the accompanying claims will occur to those skilled in the art. The invention in its broader aspects is directed to the provision of a seriesshunt type flasher wherein two pull means automatically compensate for change of. rate and of ratio with supply voltage.

The following is claimed:

1. A voltage compensated flasher comprising:

(a) a vane of resilient conducting material adapted to snap between a first and second circuit controlling position,

(b) a rst expansible pull means coupled under tension to said vane and tending when cold to maintain said vane in said rst position,

(c) a second expansible pull means connected under tension to said vane and tending when cold to snap said vane into the second of said two positions,

(d) a pair of electrical terminals for connection to an external circuit and a ballast resistor connected in series with said tirst pull means across said terminals,

said second pull means and said vane shunting said ballast resistor and first pull means in said second circuit controlling position.

2. The flasher according to claim 1 wherein said second pull ymeans is connected at opposite ends of the periphery of said vane to bow the same and carries an electrical contact at its center and wherein a fixed contact electrically connected to one of said terminals is positioned for engagement by said pull means carried contact in said second circuit controlling position, said vane being electrically connected to said other terminal.

3. The flasher according to claim 1 wherein said vane has an inherent bias therein tending to move the vane to said second position, said second pull means supplementing said bias and said first pull means opposing said bias.

4. A flasher comprising:

(a) an insulating base for carrying a pair of terminals for connection to an external circuit,

(b) a conducting frame mounted on said base and in electrical connection with one of said terminals,

(c) a resilient vane of conducting material mounted at one end of said frame,

(d) a pull ribbon connected under tension at its ends to opposite edges of said vane adjacent the unmounted end thereof,

(e) an electric contact mounted on said pull ribbon,

(f) a fixed contact mounted on said frame and aligned with said ribbon carried Contact for engagement therewith,

(g) a pull wire insulatedly anchored to said frame and coupled at one end to said vane under tension, the tension in said pull wire, when cold, tending to prevent engagement of said contacts, and

(h) a resistor connected between said pull wire and the other one of said terminals,

whereby when said contacts are separated said frame, vane, pull wire and resistor are connected across said terminals and when said contacts are in engagement said pull wire and resistor are shunted by said pull wire and resistor are shunted by said pull ribbon and contacts.

5. The asher according to claim 4 wherein said vane is generally rectangular and is transversely creased to bias the unmounted end of the vane to contact closing position, said pull ribbon when cold supplementing the bias introduced by the creasing, and wherein the tension in said pull wire acts in opposition to the bias introduced by said creasing.

6. A snap action device of the type wherein a resilient vane has an inherent deformation therein tending to move the vane to a circuit controlling position and an expansible pull means which when cold holds the vane against movement to such position and which when heated permits the vane to snap to said position, said pull means cooling in said position, the improvement comprising a second pull means connected to the vane under tension to supplement the bias introduced by the deformation, and circuit means for heating said second pull means when the vane is in said circuit controlling position, whereby when electrical energy is supplied to said device one of said pull means is expanding While the other contracts, and vice versa.

7. A series-shunt flasher having a movable circuit controlling contact carrying element, two expansible tensioned pull -rneans coupled to said element and acting oppositely thereon, a Xed contact positioned for engagement with said element carried contact, and a ballast resistor connected in series with one of said pull means, said other pull means shunting said resistor and the pull means in series therewith when said contacts are in engageinent.

References Cited by the Examiner UNITED STATES PATENTS Bell 200-122 Harmon ZOO-113 Welsh ZOO-122 Krambo et al. ZOO-113 Siiberg ZOO-113 10 BERNARD A. GILHEANY, Primary Examiner. 

7. A SERIES-SHUNT FLASHER HAVING A MOVABLE CIRCUIT CONTROLLING CONTACT CARRYING ELEMENT, TWO EXPANSIBLE TENSIONED PULL MEANS COUPLED TO SAID ELEMENT AND ACTING OPPOSITELY THEREON, A FIXED CONTACT POSITIONED FOR ENGAGEMENT WITH SAID ELEMENT CARRIED CONTACT, AND A BALLAST RESISTOR CONNECTED IN SERIES WITH ONE OF SAID PULL MEANS, SAID OTHER PULL MEANS SHUNTING SAID RESISTOR AND THE PULL MEANS IN SERIES THEREWITH WHEN SAID CONTACTS ARE IN ENGAGEMENT. 